Prevention of deterioration of hydrocarbon materials



Patented Oct. 24, 1950 PREVENTION OF DETERIORATION OF HYDROCARBON MATERIALS Lloyd 0. Morris, Bartlesville, kla., assignor' to Phillips Petroleum Company, a corporation of Delaware No Drawing. Application February 4, 1946, Serial No. 645,475

7 Claims. 1 This invention relates to the stabilization of hydrocarbon materials against deterioration. In

general, such deterioration is manifested by such developments as appearance of odor, formation of peroxides or other oxygen-containing derivatives, depositing of gummy residues, and the like. In a specific embodiment it relates to a method for prevention of the aforesaid types of deterioration in hydrocarbon susceptible to such deterioration and to a specific reagent for use in this method. In a still more specific embodiment it relates to a method for prevention of deterioration during preparation and storage of mixtures of normally liquid, saturated hydrocarbons, comprising a substantial proportion of branchedchain parafiins, which method involves the use of hydrogen sulfide as an inhibiting agent.

In recent years there has been a constantly increasing demand for hydrocarbon solvents, not only for conventional uses such as in dry cleaning, the'manufacture of paints, varnishes, waterproofing agents, etc., but also for newly developed products and processes involving specialized requirements not met by ordinary commercially available solvent materials. For example, the production of insect repellents and insecticides has created a need for an organic solvent which is capable of carrying in solution a relatively large concentration of active substance and is at the same time free from color and objectionable odor, non-toxic to man and animals, has a high flash point, and is relatively non-volatile.

It is common knowledge that many organic substances, particularly those containing unsaturated compounds, deteriorate in storage when oxygen is present, with the formation of gummy materials and oxygenated derivatives, and, in some cases, develop objectionable odors. While such deteriorative processes are more common in unsaturated compounds, even some saturated hydrocarbons, and particularly those containing tertiary carbon atoms, exhibit the tendency to develop an unpleasant odor when heated in the presence of air. Often this development of odor is accompanied by the formation of oxygenated compounds such as aldehydes, ketones, carboxylic acids, the unstable substances known as peroxides, and the like.

A common expedient in operations involving hydrocarbon materials of this nature is the employment of oxidation inhibitors such as phenols,

substituted phenols and related substances.

However, such inhibiting materials are nonvolatile and impart an instrinsic odor that is not easily removable from the oils in which they are used. Also such an inhibitor may be an undesired contaminant when the hydrocarbon material is to be used as a solvent, or the like.

I have now found that deterioration in hydrocarbon materials, and particularly in those containing highly branched paraflins, as manifested by development of odor, gummy residues, formation of oxidative substances, and the like, can be eliminated or substantially reduced by the presence of small concentrations of hydrogen sulfide. I have also found that heating and/or distillation of said hydrocarbons can be effected to provide substantially odor-free products when hydrogen sulfide, either added as such or formed in situ, is present in the process.

Obviously, in the practice of my invention, residual hydrogen sulfide and/or sulfur must be removed from the products before their final utilization. This removal may be effected by washing with an aqueous alkaline solution, by distillation, by treatment with sodium polysulfide, or by other suitable means. Furthermore, hydrocarbon stocks treated by the method herein disclosed must be substantially odor free, since the principal object of the invention is to prevent deterioration in fresh stocks.

An object of my invention is to inhibit deterioration of hydrocarbons.

Another object of my invention is to produce an odorless normally liquid hydrocarbon material.

A further object of this invention is to inhibit oxidation, by atmospheric oxygen, of paraffin hydrocarbons.

One object of my invention is to store hydrocarbons without development of odor therein.

One other object of my invention is to distill hydrocarbons, previously exposed to and/or in the presence of oxygen, without development of odor therein.

Still a further object of this invention is to inhibit oxidation of a hydrocarbon having a hydrogen atom attached to a tertiary carbon atom.

Further objects and advantages of my invention will become apparent, to one skilled in the art, from the accompanying disclosure and discussion. I

The present invention is particularly applicable to the separation, and/or to the storage, of various useful hydrocarbon fractions. An important example which may be mentioned consists in the production of solvents for dry cleaning, insecticide bases, paint and varnish thinners and the like. A readily available source of fractions boiling in the preferred range for such solvents would appear to lie in the low-odor, substantially water white alkylates produced by interaction of low-boiling isoparaffins with lowboiling olefins, some fractions of which are used in the motor fuel industry. However, the highly branched structure and consequent tendency toward deterioration and odor development during distillation and storage have heretofore been causes for difficulties in the use of this material,

amass:

3 This is believed to be due to the reactivity of so-called tertiary hydrogen atoms present in a large proportion of the isoparamns, i. e. those hydrogen atoms attached to carbon atoms which similar treatment which differed only in not adding hydrogen sulfide. The minimum amount of hydrogen sulfide which will act as a satisfactory inhibitor for such hydrocarbon materials as dilare attached to three other carbon atoms. 5 cussed herein is about 0.1 per cent of the amount In the past, low-odor fractions have been prowhich will effect a saturation of the liquid hydroduced from these alkylates, and similar hydrocarbon material at the conditions of temperature carbons comprising a highly branched molecular and pressure which would exist in the absence structure, by processes involving distillation in an of the addition of hydrogen sulfide. However, in atmosphere of inert gas. Subsequent storage of actual practice larger amounts are generally used, the fractions so produced was often accomplished up to 50-75% or more of that amount which will in containers in which oxygen was excluded by eflect complete saturation Thus, during distillablanketing with non-oxidizing inert gaseous comtion of such a hydrocarbon material hydrogen pounds or by the employment of the aforemensulfide is slowly bubbled through the distillation tioned non-volatile inhibitors. column. In open (non-pressurized) storage suf- In one general embodiment the present process ficient hydrogen sulfide will be present to produce comprises supplying hydrogen sulfide to the hyat least a faint odor. drocarbon during the heating or distilling process, An advantage of the present invention lies in either by direct injection of the gas into the ketthe simplicity of operation as compared with tie or column, or by obtaining it in situ from an processes employed when heating and distillation added substance which yields a small continuous are carried out in a normal non-oxiding atmossupply of hydrogen sulfide at the operating temphere. A further advantage lies in the excellent perature such as, for example, a mercaptan. A storage qualities of products prepared by this resulting hydrocarbon product containing dismethod, the dissolved hydrogen sulfide providing solved hydrogen sulfide, or one containing hydroinhibiting effects against deterioration over long gen sulfide introduced subsequent to distillation, periods of time. A still further advantage lies in may be stored over long periods without appreciathe broad field of materials made available for ble deterioration. When desired for utilization; the production of low-odor hydrocarbon materials highly desirable, substantially odor-free materials heretofore employable only at relatively high cost. are readily obtained by removal of the residual 0 Other advantages lie in the elimination of nonhydrogen sulfide, as by stripping of! the hydrovolatile inhibitors, blanketing gases, etc. gen sulfide in a. simple distillation column, or by While the particular embodiment described removing hydrogen sulfide by solvent or chemical herein has concerned the treatment of mixtures action. In general, my invention will be applied of saturated hydrocarbons comprising a substanto normally liquid hydrocarbons boiling below tial proportion of branched-chain paraflins, its about 500 F. at atmospheric pressure. Most of utility as applied to other types of hydro-carbons the low-odor solvents, to which the invention susceptible to similar deterioration will be apparticularly applies, will have initial boiling points parent, and such application is within the scope above about 250 F. However, the invention may of this invention. also be applied with advantage to other hydro- Example carbons, including those boiling well above 500 F. It is preferred that the hydrocarbon materials A fraction of odor-free parafiln hydrocarbons be essentially free from hydrocarbons which have boiling between 365 and 400 F. was obtained by such chemical properties that they will react with distillation of a heavy alkylate in an atmosphere the hydrogen sulfide under the conditions of its of inert gas. This heavy alkylate was obtained use. Such hydrocarbon materials can contain, from a commercial plant in which isobutane was or consist essentially of, paraflln, cycloparaflln, reacted with butenes in the presence of hydroand/or aromatic hydrocarbons and should be subflu0ric acid as the alkylation catalyst. Samples stantialiy free from olefins, acetylenes, and the of this alkylate fraction were shaken at room like. The amount of hydrogen sulfide which will temperature with air for 15 minutes, then blown give satisfactory results is not great. For examwith H2S or nitrogen, after which they were pie, I have found that if a relatively non-volatile heated under refiux for varying periods of time. isoparaifinic naphtha having an initial boiling After this heating, and subsequent washing with point between 250 and 500 F., and which has caustic, the degree of odor development was obpreviously been exposed to atmospheric oxygen, served and the samples were tested for the pressubsequently is substantially saturated with hyence of peroxides. The results of these tests, todrogen sulfide at atmosphere temperature and gether with a test on a sample which had been pressure and then heated briefly to its boiling subjected to air blowing only, are shown in the point, it will still retain a faint odor of hydrogen following tabulation:

Peroxide Heating Temp. Odor gg gfl g H101) Wain flit: M it tilts-ruse: 113 Original Alkylate+H|8 --d0 3 Original 1m+ms a Original Alkylate+Ha8 3 orisimlmylm+m 1:1

sulfide when cooled back to atmospheric tempera- It will be understood that various modifications ture to F.) and will be inhibited against of my invention can be readily practiced, by one odor-development by oxidation. 0n the other skilled in the art, without departing from the hand, another sample of the same naphtha has spirit of the disclosure and teachings, or without been found to develop an offensive odor after 75 departing from the scope of the claims.

Iclaim: V 1. An improved process for storing and subsequently'making available for use an odorless, parafiinic hydrocarbon liquid, which comprises storing in the presence of added hydrogen sulfide a parafiinic hydrocarbon liquid boiling .between 250 and 500 F. and produced by reacting isobutane with butenes under alkylation conditions, said hydrogen sulfide being present in said paraffinic hydrocarbon liquid in an amount equal to at least 0.1 per cent of the amount necessary to saturate said paraifinic hydrocarbon liquid with hydrogen sulfide, and at the end of a storage period removing from said paraifinic liquid said hydrogen sulfide.

2. An improved process for storing and subsequently making available for use an odorless,

.parafiinic hydrocarbon liquid, which comprises storing in the presence of added hydrogen sulfide a liquid paraflinic alkylate fraction produced by reacting low-boiling isoparafllns with lowboiling olefins under alkylation conditions, and at the end of a storage period removing from said paraflinic liquid said hydrogen sulfide.

3. An improved process for storing and sub-' sequently making available for use an odorless, paraflinic hydrocarbon liquid, which comprises storing in the presence of added hydrogen sulfide a liquid paraifinic alkylate fraction having an initial boiling point above 250 F. and an end point below 500 F. and produced by reacting lowboiling isoparaflins with low-boiling olefins under alkylation conditions, said hydrogen sulfide being present in said alkylate fraction in an amount equal to at least 0.1 per cent of the amount necessary to saturate said alkylate fraction with hydrogen sulfide, and at the end of a storage period liquid saturated hydrocarbon material during distillation, which comprises distilling in the presence of added hydrogen sulfide an alkylate fraction having an initial boiling point above 250 F. and an end point below 500 F. and produced by reacting low-boiling isoparaffins with low-boiling olefins under alkylation conditions, said hydrogen sulfide being present in an amount equal to at least 0.1 per cent of the amount necessary to saturate .said alkylate fraction with hydrogen sulfide.

6. An improved process for storing and subsequently making available for use an odorless, parafiinic hydrocarbon liquid, which comprises storing in the presence of added hydrogen sulfide a liquid parafiinic alkylate fraction having an initial boiling point above 250 F. and an end point below 500 F. and produced by reacting low-boiling isoparafiins with low-boiling olefins under alkylationconditions, said hydrogen sulfide being present in said alkylate fraction in an amount equal to' at least 0.1 per cent and no more than 75 percent of the amount necessary to saturate said alkylate fraction with hydrogen sulfide, and at -the end of a storage period removing hydrogen sulfide from said alkylate fraction.

7. An improved method of inhibiting formation of odoriferous compounds in a normally liquid saturated hydrocarbon material during distillation, which comprises distilling in the presence of added hydrogen sulfide an alkylate fraction having an initial boiling point above 250 F. and an end point below 500 F. and produced by reacting low-boiling isoparaifins with low-boiling olefins under alkylation conditions, said hydrogen sulfide being present in an amount equal to at least 0.1 per cent and no more than 75 per cent of the amount necessary to saturate said alkylate fraction .with hydrogen sulfide.

LLOYD C. MORRIS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Wolk Sept. 17, 1946 

4. AN IMPROVED METHOD OF INHIBITING FORMATION OF ODORIFEROUS COMPOUNDS IN A NORMALLY LIQUID SATURATED HYDROCARBON MATERIAL DURING DISTILLATION, WHICH COMPRISES DISTILLING IN THE PRESENCE OF ADDED HYDROGEN SULFIDE A LIQUID PARAFFINIC ALKYLATE FRACTION PRODUCED BY REACTING LOW-BOILING ISOPARAFFINS WITH LOW-BOILING OLEFINS UNDER ALKYLATION CONDITIONS. 